Mercury arc device



Sept 25,-1945- L. M. WITTLINGER :rm.

MERCURY ARC DEVICE Filed Aug. 30, 1943 29 (0/? j w attgrnegs Patented Sept. 25, 1945 MERCURY ARC DEVICE Leonard M. Wittlinger, Flint, Mich., and William Ky.-,- as'signors to General Detroit, Mich, a corpora- S. Brian, Owenbom, Motors Corporation,

tion of Delaware Application August 30, 1943, Serial No. 500,486 10 Claims. (Cl. 315-56) This invention relates to mercury are means and more specifically to mercury are means as a source of luminescent rays. There have recently been a number of instances in which it is desirable to provide and utilize rays of the ultraviolet type for various purposes, such, as, for example, the use of a mercury arc generator of ultraviolet rays whereby the same may be projected in a beam either to locate objects covered with luminescent material, such as road markers so that field maneuvers may be made under cover of darkness without disclosing such movement to the enemy, or signaling between points, using such ultraviolet or substantially invisible rays projected in a beam from one point to another which Would not be discernible for enemy interception. These are, of course, only two examples; many other uses are to be found for such equipment.

It is therefore an object of our invention to provide a satisfactory source for ultraviolet rays.

It is a further object of our invention to provide a relatively small tube capable of generating rays of ultraviolet wave length.

It is a still further object of our invention to provide a mercury arc tube in which the inner surface is not discolored after periods of operation.

With these and other objects in view, which will become apparent as the specification proceeds, the embodiments of our invention will be best understood by reference to the following specification and claims and the illustrations in the accompanying drawing, in which:

Figure 1 shows a vertical section through a tube embodying one form of our invention; and

Figures 2, 3, 4 and 5 are similar vertical sections showing different modified forms of ou invention.

The general type of tube disclosed herein is that having in reality two different sections: a low voltage and a high voltage section, the low voltage providing an. automatic interrupter pair of electrodes which periodically and successively interrupt a low voltage circuit, and the second or high voltage portion embodying an electrode capable of drawing an are from the upper surface of a mercury pool, which latter portion of course provides the main source for ultraviolet rays. This general type has been disclosed in a patent to Brian, No. 2,289,623, issued July 14, 1942, and entitled Mercury light tube. 'However, in the earlier forms of this device it was found that the inner surface of the envelope which enclosed the arc section began to darken after the tube had been in use for a little time. After some study as to what caused this darkening, which of course interfered considerably with the amount of ultraviolet rays transmitted through the tube, itwas determined that this was due to small particles of carbon eroded away from the carbon electrode of the interrupter section of the tube which floatedto the top of the mercury pool and were then splattered onto the inner surface of the tube by the arc. In aneffort to prevent these small eroded carbon particles from reaching the upper surface of the mercury pool, the present constructions were evolved.

Referring now more specifically to Figure 1,

there is shown therein an enclosing envelope 2 which'carries at its upper end a sealed-in electrode 4 and in one side a second electrode 6. A third electrode 8 is supported in the lowerpo'rtion of the envelope and is stacked into a small carbon disc l0 forming the lower electrode of the interrupter section. Surrounding this carbon electrode I0 is a small ceramic disc l2 rigidly supported in the interior of the envelope. A second internal envelope l4 integral with the base of the outer envelope 2 and substantially concentric with and spaced from the vertical portion extends up approximately one-half the full length of the interior and totally encloses the ceramic disc and carbon electrode in. In one side of thisinner envelope there is provided an opening l6 whereby the mercury [8 in the large envelope may how in and out of the inner envelope entirely covering the same and extending up a substantial distance above the upperv end to within a relatively short distance of the lower end of the electrode 4. A small up-turned tube 20 i supported within the inner envelope l4 and extends upabove the opening it to provide a bafiie for the carbon particles as they ascend in the mercury. v

Through the exterior circuit between electrodes 6 and 8, which is fully disclosed in the above identified patent, low voltage power is supplied to the tube and current flows between them from electrode 6 through the mercury bath l8 between the large and small envelopes through the mercury in the opening it through the mercury within the inner envelope M to the carbon electrode l0' and thus to the electrode 8. As described in the patent, when this current intensity is sufficient to heat the mercuryin contact with the carbon III, that mercury vaporizes and flashes off the surface of the carbon electrode to interrupt the circuit. whereupon, since the source of heat has now disappeared, he mercu'ry vapor condenses to reform the same, thus they are lighter than mercury,

mercury I8 from upper electrode 4.

I mit a maximum portion of 2 providing an automatic continuous interruption.

In this operation, however, the upper surface of the mercury begins to erode and small particles of the carbon are broken away, and since tend to rise to the surface of the mercury pool. Thus they ascend through the small tube 20 to eventually contact the upper inner surface of the innerenvelope l4 and are unable to reach the upper surface of the which an arc is drawn to the hon particles and the inner surface of the glass will not discolor but will remain clear and transthe ultraviolet rays generated by the are over a Figure 2 shows a second form of trap for preventing the small carbon particles from rising to the upper surface or are surface of the mercury. In this instance the same main electrodes 4, 6, 8 and ill are present in their same. respective positions. The envelope 2 in this case, however, supports a larger ceramic disc. l2 in its base and has ex.- tending across slightly below the middle a bulbous or spherical baffle 22 which is supported by the sides of the envelope and extends entirely between them. One side of this spherical ,baflle has an opening 24 therein through whichmercury 18 can flow from the upper portion of the envelope to the lower portion. This opening, how- .ever, is directed downward from and is considerably below the top of'the spherical ball 22. In like manner. any carbon particles eroding from the electrode l whichtend to rise to the top of the mercury will be trapped inthe upper portion of .the spherical ball 22 and will be prevented from reaching the upper surface of the mercury l8 from which the electrode 4 drawsanarc.

Figure 3 shows a further modified form which is substantially the same as Figure 2 except that instead of a spherical baiileacross the envelope, one of a substantially pyramidal form is utilized. As shown in this figure, the -pyramidal baflle 26 is shown extending between the two side walls of the envelope 2"" and in this instance'is -much lower than that in Figurefl, the base of the pyramid being substantially in alignment withthe upper surface ofthe disc l2. A-small opening 28 is provided in inter-connection of the mercury outside andinside the baffle portion. Its action of course is the same as that previously described. w In Figure 4 thereis shown'a still further modification in which a small cylindrical housing 30 is shown immediately. over thecarbon electrode. said cylindrical housing terminating in arsemilspherical dome 32 for the collection .of the-carbon particles and being mounted directly on the upper surface of a-base34 which surrounds and holds in place the carbon electrode l0. The lower portion ofthe housing 30 is slotted as shown at 36 to allow mercury to flow. in through the slots and also. is provided with an opening -38- on one side -to further-allow inter-communication between the two mercury pools. in this instance, of course, the small carbon particles eroding from the upper surface of electrode will be trapped in the dome-shaped portion 32 of the housing. ,r

Figure 5 shows quite a differentpform in which the envelope 2'," is separated into two major portions by a spherical bafile40. thus providing an upper and a lower chamber. In the lowercham- 'ber, there aretwo main electrodes 6 and 8', the latter being electrically connectedto a long carthe horizontal the side of the pyramid for Thus the upper surface of the mercury will be kept clean from any small car-'- long period of time.

r be eliminated. The are "velope 2' Within this housing ticn, and extending the housing 4i3'to the interior of the lower sec- -no carbon particles from bon electrode H3 extending up into the chamber and surrounded by glass sleeve portion 42 eventually terminating in a beveled face 44. This chamber is filled with a mercury pool 46 which completes the electrical circ t from the beveled face 44 to the electrode 6' to provide interrupter action. Mounted on the upper central surface of the spherical-baffle "40. and within the upper chamber soprovided is a second cylindrical housing 48 of smaller diameter than the outer enand spaced from its inner surface. 48 there is a small mercury which of course resides in the lower porthrough from the interior of pool 50 tion of the envelope 2" is a metallic conducting electrode 52 adapted to contact both mercury pools 59 and 45 and-to conduct current from one to the other.

Theupper portion of the envelope 2" supports as before an electrode 4 which in this case extends down into the interior cylindrical member 48 to a definite spaced distance from the small mercury pool 55!. Since therefore the two sections of the tube arenow definitely separated into an interrupter portionand .an arc portion, the surface 44 can possibly be carried up to the upper or are portion within the housing 48and therefore the coating or darkening of a the internal surface thereof through the splattering of carbon particleswill will be drawn inthis instance between electrode 4 and mercury pool 50 which is in conductiverelation with electrode 6 through contact rod 52 and mercury pool 46. v We claim; g .7

1. In a device of the class described, a housing, a carbon electrode supported in the housing. a mercury pool partially filling the housing in contact with said electrode and forming a part-oi the circuit therewith and baflle .means to trap carbon particleseroded' away from. the carbon electrode through use and stop them from reach ing the upper surface of the mercury pool. v V V y 2. In a device of the class described, a housing, a carbon electrode supported in "the, housing, a mercury pool partially filling the housing in contact with said electrode and forming a part of the circuit therewith, and spherical baflling means mounted in the housing below the surface level of the mercury trapping any eroded carbon particles from the j carbon electrode and stopping them from rising to the surface of the mercury.

3. In a device of 'th'e cla'sfs'described.a housing, an electrode' formed of a materiallwhich erodes away in small particles upon current flow therethrough supported by said housingga mercury 7 pool partially filling the housing in contact with said electrode and forming a part of a. circuit therewithv and trapping means carried by said housing to stop any eroded electrode particles from; reaching the surface of the mercury pool. v 4. In a device of the class described, a hollow envelope of insulating material, a body i Inercury partially fillin Said envelope, ,an electrode in thelower portionof h th me c which el qtr defs d way upon usage whereby. small particles thereof will tend to rise to the surface of the mercury and spherical .bailling meansacross the envelopebelow thesurface of the mercury to trap said particles and stopthem from getting to the surface of the mercury, v H H v 5.111 a device of the class described, a. hollow envelope of ,insulating materialpa plurality of said envelopein contact 7 electrodes in one portion of the envelope, one of which electrodes i formed of carbon, a pool of mercury partially filling said envelope and completing the circuit between the electrodes to form an interrupter therewith, a further electrode supported in the envelope in spaced relation to the mercury and adapted to draw an arc from the mercury surface and baffling means trapping particles of carbon eroded from the carbon electrode due to interrupter current flow.

6. In a device of the class described, a hollow envelope of insulating material, a plurality of electrodes in one portion of the envelope, one of which electrodes is formed of carbon, a pool of mercury partially filling said envelope and completing the circuit between the electrodes to form an interrupter therewith, a further electrode supported in the envelope in spaced relation to the mercury and adapted to draw an are from the mercury surface, and bailing means across the envelope below the surface of the mercury to trap eroded carbon particles.

7. In a device of the class described, a hollow envelope of insulating material, a plurality of electrodes in one portion of the envelope, one of which electrodes is formed of carbon, a pool of mercury partially filling said envelope and completing the circuit between the electrodes to form an interrupter therewith, a further electrode supported in the envelope in spaced relation to the mercury and adapted to draw an arc from the mercury surface, and spherical bailing means across the envelope below the surface of the mercury having an opening therethrough below the top portion whereby eroded carbon particles are trapped in the concave top and a continuous mercury connection is provided through the openmg.

8. In a device of the class described, an envelope of insulating means, a pair of electrodes supported in spaced relation in one part of the envelope, one of said electrodes being formed of carbon, a pool of mercury in the envelope bridging the electrodes and forming therewith an interrupter, a third electrode supported in a further portion of the envelope and providing arcin means and bathing means trapping eroded carbon particles from the interrupter section to stop them from reaching the arc section and being splattered onto the envelope surface to darken the same.

9. In a device of the class described, an insulating envelope, a partition dividing the envelope into two chambers, a pair of electrodes supported in spaced relation in one chamber, one of said electrodes being formed of carbon, a pool of mercury in said first chamber bridging said electrodes to form therewith an interrupter, a third electrode supported in the second chamber and conductive means extending through the partition to carry current from the first to the second chamber to cooperate with the third electrode to form an arc therewith.

10. In a device of the class described, an insulating envelope, a partition dividing the en-- velope into two chambers, a pair of electrodes supported in spaced relation in one chamber, one of said electrodes being formed of carbon, a pool of mercury in said first chamber bridging said electrodes to form therewith an interrupter, a third electrode supported in the second chamber, conductive means extending through the partition to carry current from the first to the sec ond, chamber to cooperate with the third electrode to form an arc therewith and a small body of mercury in the second chamber to form part of the circuit between the third electrode and the conductive means.

LEONARD M. WITTLINGER. WILLIAM S. BRIAN. 

